With a view to suppressing power consumption of semiconductor integrated circuits, there is a need for suppressing power consumption of individual transistors, which are the constituting elements.
As a method for achieving this object, research and development are pursued for suppressing a power required for ON-OFF switching operations of the transistors by providing a steep current change rate in a region (subthreshold region) lower than or equal to a threshold voltage that defines the switching operations. The current change rate in the subthreshold region is an index for a gate voltage (S factor) required for changing a current value by one digit. A lower current change rate enables a steeper switching operation.
However, in a typical transistor configuration, the current change rate in the subthreshold region at room temperature is higher than or equal to 60 mV/decade theoretically. Therefore, there is a problem that a steeper characteristic lower than this cannot be obtained (see, e.g., Yuan Taur and Tak H. Ning, Fundamentals of MODERN VLSI DEVICES, Cambridge University Press 1998, p. 128).
Hence, currently, development of a novel transistor having a steep characteristic represented by the current change rate of lower than 60 mV/decade is sought after based on a configuration different from typical transistors.
As such a novel transistor, there is proposed, for example, a tunneling field-effect transistor utilizing quantum tunneling (W. Y. Choi, et. al., Electron Device Letters 28 (2007), p. 743).
However, the proposed tunneling field-effect transistor has a problem of requiring a high gate voltage for its operation in order to apply a high electric field to a tunnel junction to modulate bands and induce tunneling transportation of carriers, thus failing to realize low power consumption.
Hence, currently, research and development of a novel transistor that is low power-consuming and aims to obtain a steep current change rate of lower than 60 mV/decade in the subthreshold region at room temperature are sought after from various aspects.